Reading specifications and tolerances

Skills you'll practise

• Calculate the upper and lower limits from bilateral, unequal, unilateral, limit-dimension and percentage tolerances
• Find which tolerance applies to a dimension that has none written beside it, using the drawing's general tolerance note
• Decide whether a measured value is in or out of tolerance without rounding it to fit
• Recognize reference and basic dimensions and ask quality before inspecting them as if they were toleranced
• Stop and escalate when the drawing, work order and instruction revisions don't agree

Course outline

1. 1.Reading specifications and tolerancesVideo · 2 min
2. 2.Nominal, tolerance and limitsLesson · 17 min
3. 3.Which tolerance applies?Lesson · 16 min
4. 4.Making honest in/out decisionsLesson · 17 min
5. 5.Reading specifications and tolerances: knowledge checkKnowledge check · 17 questions
6. 6.Reading specifications and tolerances: practical exerciseKnowledge check · 1 question
7. 7.Final exam9 questions · passing it completes the course, so people who already know the material can test out

Sources it draws on

The lessons and questions are written from these references, so learners can go back to the original.

• ASME Y14.5: Dimensioning and Tolerancing (US drawing practice; ISO GPS standards are the international equivalent)
• ISO 2768-1: General tolerances for linear and angular dimensions without individual tolerance indications (classes f, m, c, v)
• ISO 9001:2015 Quality management systems: Requirements (clauses cited: 7.5 documented information, 8.5.2 identification and traceability, 8.7 control of nonconforming outputs)
• Your site's quality manual, inspection plans, drawings and nonconformance procedure (these govern)